It is proposed that changes in transport characteristics of lipid bilayer membranes associated with the presence of pesticides in the membrane-electrolyte system be investigated. The specific molecular mechanisms underlying three groups of phenomena will be considered: 1. The interaction of pesticides with continuous lipid membranes involving partition-diffusion processes. 2. The interaction of pesticides with porous lipid membranes. 3. The mechanisms controlling ionic channels in excitable membranes in the presence of insecticides. Current-voltage characteristics and membrane potentials will be measured under various conditions and the experimental results will be compared with the predictions of available transport models proposed to explain the effect of known membrane modifiers on membrane properties. In some cases the direct current information will be supplemented by a-c measurements of capacitance and conductance. In particular, those questions which concern lipid specificity and the modification of ionic selectivity will be investigated in detail.